1. Field of the invention
The field of the invention relates to bags or sacks which may be used as liners for trash cans and the like.
2. Brief description of the related art
Bag-type liners are frequently used within trash cans for protecting the cans and to facilitate removal of the contents therefrom. The materials from which a liner is made and the manner in which it is constructed depends upon the intended use thereof. Liners intended for grass clippings and garden debris need not be particularly leak-proof as the consequences of leakage are insignificant. Where such liners are used for industrial waste, prevention of leakage is very important, even where the waste is not particularly hazardous.
Various approaches have been taken for manufacturing and sealing liners in order to prevent leakage therefrom. An early form of such liners was made from an unfolded tube. The entire width of the bottom of the tube was sealed with either a single or a double seal bar. This construction is referred to as the "lay flat" construction. In order to seal more bags in production, a gusseted bag has been produced. The seal across a gusseted bag does not hold up well under wet load testing, however.
Folded end seal bags have been found to provide a strong seal as the forces exerted upon the bottom of the bag are relatively uniformly distributed. Such bags or liners are formed by first folding the two outside edges of a tube towards the middle, then folding one resulting edge over the other. The seal extending across such bags is through eight layers.
"Star seals" are formed by folding the right edge over the left edge of a tube, and then again folding the right edge over the left edge. This type of seal also provides for stress distribution.
The presence of wrinkles in thermoplastic films, and particularly high molecular weight films, can cause deterioration of the seals at the bottoms of liners formed from such films. Penetration of the end seals by such wrinkles can result in leakage. Reduction of the number of wrinkles is only a partial solution to this problem.